Modern agricultural harvesters, such as combine harvesters and forage harvesters, are heavy pieces of machinery, which in many cases have to travel over public roads from one field to another. In many countries regulations exist that prescribe a maximum axle load for vehicles travelling on public roads. The current developments in agricultural harvesters lead to an increase of the axle loads of these harvesters. In particular when a header is attached to the agricultural harvester during road transport, the front axle load can reach levels which are close to or even above the maximum allowable axle load for public roads.
It is known from the prior art to provide one or more support wheels on the front parts of the agricultural harvester. These support wheels are generally connected to the header or to the feeder of the agricultural harvester.
It is known to use support wheels that are in contact with the ground during road transport as well as during the harvesting operation on the field, and alternatively, to use support wheels that are in contact with the ground during road transport or during the harvesting operation on the field.
Generally, it is disadvantageous if the support wheels contact the ground during harvesting, so when the agricultural harvester is driven over the field. Support wheels that contact the ground during harvesting have to be rather large in order to avoid undesired compacting of the ground and the undesired formation of ruts in the field, which is impractical and expensive.
If the support wheels are designed to be in contact with the ground during either road transport or during harvesting (when the harvester is driven over the field), provisions have to be made to avoid ground contact of the support wheels when such ground contact is not desired.
EP1046329 discloses to remove the support wheels entirely when the harvester is made ready for harvesting, and to mount the support wheels again when the harvester is made ready for driving on the road.
WO2010/130745 discloses a harvester which requires the use of support wheels during harvesting, but not during road transport. In this harvester, the support wheels are mounted on a frame which is pivoted inwards, i.e. towards the center line of the harvester parallel to the driving direction of the harvester, when the harvester is made ready for road transport. In this road transport mode, the axis of the support wheels extends substantially parallel to the main driving direction of the harvester, in a substantially horizontal plane. The main driving direction of the harvester is straight ahead.
Removing the support wheels after use and mounting them when they are needed again is highly impractical and labor-intensive. There is limited space available for a frame in the vicinity of the header and/or feeder, and a complex movement may be required to transfer the support wheels from their position during road transport to their position during field operation and/or vice versa. In addition, the bearings of the support wheels may be susceptible of damage caused by vibrations when the support wheels are not in contact with the ground.